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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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 */

package java.beans;

import java.util.EventObject;

/**
 * A "PropertyChange" event gets delivered whenever a bean changes a "bound"
 * or "constrained" property.  A PropertyChangeEvent object is sent as an
 * argument to the PropertyChangeListener and VetoableChangeListener methods.
 * <P>
 * Normally PropertyChangeEvents are accompanied by the name and the old
 * and new value of the changed property.  If the new value is a primitive
 * type (such as int or boolean) it must be wrapped as the
 * corresponding java.lang.* Object type (such as Integer or Boolean).
 * <P>
 * Null values may be provided for the old and the new values if their
 * true values are not known.
 * <P>
 * An event source may send a null object as the name to indicate that an
 * arbitrary set of if its properties have changed.  In this case the
 * old and new values should also be null.
 */
public class PropertyChangeEvent extends EventObject {

  private static final long serialVersionUID = 7042693688939648123L;

  /**
   * Constructs a new {@code PropertyChangeEvent}.
   *
   * @param source the bean that fired the event
   * @param propertyName the programmatic name of the property that was changed
   * @param oldValue the old value of the property
   * @param newValue the new value of the property
   * @throws IllegalArgumentException if {@code source} is {@code null}
   */
  public PropertyChangeEvent(Object source, String propertyName,
      Object oldValue, Object newValue) {
    super(source);
    this.propertyName = propertyName;
    this.newValue = newValue;
    this.oldValue = oldValue;
  }

  /**
   * Gets the programmatic name of the property that was changed.
   *
   * @return The programmatic name of the property that was changed. May be null if multiple
   * properties have changed.
   */
  public String getPropertyName() {
    return propertyName;
  }

  /**
   * Gets the new value for the property, expressed as an Object.
   *
   * @return The new value for the property, expressed as an Object. May be null if multiple
   * properties have changed.
   */
  public Object getNewValue() {
    return newValue;
  }

  /**
   * Gets the old value for the property, expressed as an Object.
   *
   * @return The old value for the property, expressed as an Object. May be null if multiple
   * properties have changed.
   */
  public Object getOldValue() {
    return oldValue;
  }

  /**
   * Sets the propagationId object for the event.
   *
   * @param propagationId The propagationId object for the event.
   */
  public void setPropagationId(Object propagationId) {
    this.propagationId = propagationId;
  }

  /**
   * The "propagationId" field is reserved for future use.  In Beans 1.0
   * the sole requirement is that if a listener catches a PropertyChangeEvent
   * and then fires a PropertyChangeEvent of its own, then it should
   * make sure that it propagates the propagationId field from its
   * incoming event to its outgoing event.
   *
   * @return the propagationId object associated with a bound/constrained property update.
   */
  public Object getPropagationId() {
    return propagationId;
  }

  /**
   * name of the property that changed.  May be null, if not known.
   *
   * @serial
   */
  private String propertyName;

  /**
   * New value for property.  May be null if not known.
   *
   * @serial
   */
  private Object newValue;

  /**
   * Previous value for property.  May be null if not known.
   *
   * @serial
   */
  private Object oldValue;

  /**
   * Propagation ID.  May be null.
   *
   * @serial
   * @see #getPropagationId
   */
  private Object propagationId;

  /**
   * Returns a string representation of the object.
   *
   * @return a string representation of the object
   * @since 1.7
   */
  public String toString() {
    StringBuilder sb = new StringBuilder(getClass().getName());
    sb.append("[propertyName=").append(getPropertyName());
    appendTo(sb);
    sb.append("; oldValue=").append(getOldValue());
    sb.append("; newValue=").append(getNewValue());
    sb.append("; propagationId=").append(getPropagationId());
    sb.append("; source=").append(getSource());
    return sb.append("]").toString();
  }

  void appendTo(StringBuilder sb) {
  }
}
